Funding was provided by the University of Utah. We would like to thank Dr. J. Xu (UC Merced) and Dr. B.J.N Reddy (UC Irvine) for useful discussions.

1. Installation of 980 nm Wavelength Single Optical Trap
<ol>
	<li>Optical trapping at 980 nm wavelength is often optimal for biophysics experiments and inexpensive laser diodes are readily available with power output as high as 300 mW. It is preferable for a diode laser to be pigtailed with polarization-preserving single mode fiber with a known mode field diameter. The fiber needs to be sufficiently long to act as a mode filter and is typically terminated with either a FC/PC or FC/APC connector. Of these, FC/APC is pr...

<ol>
	<li>Svoboda, K., Block, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biological+applications+of+optical+forces.">Biological applications of optical forces.</a> Annu. Rev. Biophys. Biomol. Struct. 23, 247-285 (1994).</li><li>Ashkin, A., Schutze, K., Dziedzic, J. M., Euteneuer, U., Schliwa, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Force+generation+of+organelle+transport+measured+in+vivo+by+an+infrared+laser+trap.">Force generation of organelle transport measured in vivo by an infrared laser trap.</a> Nature. 348, 346-348 (1990).</li><li>Shubeita, G. T., Tran, S. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Consequences+of+motor+copy+number+on+the+intracellular+transport+of+kinesin-1-driven+lipid+droplets.">Consequences of motor copy number on the intracellular transport of kinesin-1-driven lipid droplets.</a> Cell. 135, 1098-1107 (2008).</li><li>Polin, M., Ladavac, K., Lee, S. H., Roichman, Y., Grier, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimized+holographic+optical+traps.">Optimized holographic optical traps.</a> Opt Express. 13, 5831-5845 (2005).</li><li>Sun, B., Roichman, Y., Grier, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Theory+of+holographic+optical+trapping.">Theory of holographic optical trapping.</a> Opt. Express. 16, 15765-15776 (2008).</li><li>Moffitt, J. R., Chemla, Y. R., Smith, S. B., Bustamante, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+optical+tweezers.">Recent advances in optical tweezers.</a> Annu. Rev. Biochem. 77, 205-228 (2008).</li><li>Grier, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+revolution+in+optical+manipulation.">A revolution in optical manipulation.</a> Nature. 424, 810-816 (2003).</li><li>Neuman, K. C., Block, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+trapping.">Optical trapping.</a> Rev. Sci. Instrum. 75, 2787-2809 (2004).</li><li>Sheetz, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laser+tweezers+in+cell+biology.">Laser tweezers in cell biology.</a> Introduction. Methods Cell Biol. 55, xi-xii (1998).</li><li>Spudich, J. A., Rice, S. E., Rock, R. S., Purcell, T. J., Warrick, H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+traps+to+study+properties+of+molecular+motors.">Optical traps to study properties of molecular motors.</a> Cold Spring Harb. Protoc. 2011, 1305-1318 (2011).</li><li>Visscher, K., Gross, S. P., Block, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Construction+of+multiple-beam+optical+traps+with+nanometer-resolution+position+sensing.+Selected+Topics+in+Quantum+Electronics.">Construction of multiple-beam optical traps with nanometer-resolution position sensing. Selected Topics in Quantum Electronics.</a> IEEE Journal of. 2, 1066-1076 (1996).</li><li>Valentine, M. T., Guydosh, N. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precision+steering+of+an+optical+trap+by+electro-optic+deflection.">Precision steering of an optical trap by electro-optic deflection.</a> Opt Lett. 33, 599-601 (2008).</li></ol>

The authors have nothing to disclose.

We have constructed an instrument which combines two optical traps of different types (Figure 1) to provide separate trapping facilities for object manipulation and measurement. The "conventional" optical trap is built around a 980 nm diode laser. This beam is expanded, steered and then injected into our inverted microscope ("light red" beam in Figure 1). The holographic optical trap is built around a 1,064 nm DPSS laser. The beam is expanded to fit the size of the spatial light modulato...

Optical trapping is one of the key techniques in biophysics 6. A crucial advancement in optical trapping has been the development of holographic traps which allow for the creation of three-dimensional trapping patterns rather than conventional point traps 7. Such holographic traps possess the advantage of versatility in positioning of refractive objects. However conventional traps can be easily aligned to be more symmetric than commercially available holographic kits. They also allow for fast precise tracking of the trapped objects. Here we describe a system (Figure 1) which combines the two trapping approaches in one instrument and allows the user to exploit the benefits of both as appropriate.
The general considerations of constructing optical traps (based on single or multiple laser beams) are discussed in detail elsewhere 8-10. Here, we outline the considerations specific to our setup and provide detail of our alignment procedure. For instance, systems with two optical trapping beams have been described before (e.g. ref. 11), typically using one laser beam for trapping a refractive object and using the other (intentionally low power beam) for decoupled readout of the position of the trapped object. Here however, both laser beams need to be high powered (300 mW or higher) because both are to be used for trapping. For measurements of biological systems, the lasers used for trapping should optimally fall within a specific NIR window of wavelength to minimize light induced protein degradation 1. Here we have chosen to use 980 nm diode and 1,064 nm DPSS lasers because of their low cost, high availability and ease of operation.
We have also chosen to use a spatial light modulator (SLM) to create and manipulate multiple traps simultaneously in real time 4,5. These devices are commercially available however their integration into a complete setup presents unique challenges. Here we describe a practical approach which addresses these potential difficulties and provides a highly versatile instrument. We provide an explicit example for the specific setup described which can be used as a guide for modified designs.

<table border="1">
	<tbody>
		<tr>
			<td>Equipment</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Optical table</td>
			<td>Newport corporation</td>
			<td>ST-UT2-56-8</td>
			<td>Irvine, CA</td>
		</tr>
		<tr>
			<td>Microscope, Inverted, Eclipse Ti</td>
			<td>Nikon USA</td>
			<td>MEA53220</td>
			<td>Melville, NY</td>
		</tr>
		<tr>
			<td>Plan apo 100X oil objective (1.4 NA)</td>
			<td>Nikon USA</td>
			<td>MRD01901</td>
			<td>Melville, NY</td>
		</tr>
		<tr>
			<td>Oil condenser Lens 1.4 NA</td>
			<td>Nikon USA</td>
			<td>MEL41410</td>
			<td>Melville, NY</td>
		</tr>
		<tr>
			<td>EMCCD camera</td>
			<td>Andor technology USA</td>
			<td>Ixon DU897</td>
			<td>South Windsor, CT</td>
		</tr>
		<tr>
			<td>1/3" CCD IEEE1394 camera</td>
			<td>NET USA Inc</td>
			<td>Foculus FO124SC</td>
			<td>Highland IN</td>
		</tr>
		<tr>
			<td>Laser, TEM00, SLM, 1,064 nm wavelength</td>
			<td>Klastech Laser Technologies</td>
			<td>Senza-1064-1000</td>
			<td>Dortmund; Germany</td>
		</tr>
		<tr>
			<td>laser diode, TEM00, SLM, 980 nm</td>
			<td>Axcel Photonics</td>
			<td>BF-979-0300-P5A</td>
			<td>Marlborough, MA</td>
		</tr>
		<tr>
			<td>laser diode mount</td>
			<td>ILX Lightwave</td>
			<td>LDX-3545, LDT-5525, and LDM-4984</td>
			<td>Bozeman, MT</td>
		</tr>
		<tr>
			<td>adjustable fiber ports</td>
			<td>Thorlabs</td>
			<td>PAF-X-11-B</td>
			<td>Newton, NJ</td>
		</tr>
		<tr>
			<td>holographic system</td>
			<td>Arryx</td>
			<td>HOTKIT-ADV-1064</td>
			<td>Chicago, IL</td>
		</tr>
		<tr>
			<td>holographic mirror</td>
			<td>Boulder Non-linear Systems</td>
			<td>this is a part of HOTKIT-ADV-1064</td>
			<td>Lafayette, CO</td>
		</tr>
		<tr>
			<td>Calcite polarizer</td>
			<td>Thorlabs</td>
			<td>GL10-B</td>
			<td>Newton, NJ</td>
		</tr>
		<tr>
			<td>half-wave plate</td>
			<td>Thorlabs</td>
			<td>WPH05M-1064</td>
			<td>Newton, NJ</td>
		</tr>
		<tr>
			<td>Polarizer rotation mount</td>
			<td>Thorlabs</td>
			<td>PRM1</td>
			<td>Newton, NJ</td>
		</tr>
		<tr>
			<td>half-wave plate rotation mount</td>
			<td>Thorlabs</td>
			<td>RSP1</td>
			<td>Newton, NJ</td>
		</tr>
		<tr>
			<td>Shutter</td>
			<td>Thorlabs</td>
			<td>SH05</td>
			<td>Newton, NJ</td>
		</tr>
		<tr>
			<td>dichroic mirrors (DM2 &amp; DM3); 45&deg; AOI</td>
			<td>Chroma Technology</td>
			<td>t750spxrxt</td>
			<td>Bellows Falls, VT</td>
		</tr>
		<tr>
			<td>dichroic mirror (DM1); 45&deg; AOI</td>
			<td>Thorlabs</td>
			<td>DMSP1000R</td>
			<td>Newton, NJ</td>
		</tr>
		<tr>
			<td>custom mechanical adapter</td>
			<td>Thorlabs</td>
			<td>SM1A11 and AD12F with enlarged inner bore</td>
			<td>Newton, NJ</td>
		</tr>
		<tr>
			<td>notch filter</td>
			<td>Semrock</td>
			<td>FF01-850/310-25</td>
			<td>Rochester, NY</td>
		</tr>
		<tr>
			<td>Acousto-Optic deflector (2-axis)</td>
			<td>intraAction</td>
			<td>DTD-584CA28</td>
			<td>Bellwood, IL</td>
		</tr>
		<tr>
			<td>goniometric stage</td>
			<td>New Focus</td>
			<td>9081</td>
			<td>Santa Clara, CA</td>
		</tr>
		<tr>
			<td>60 mm steering lenses</td>
			<td>Thorlabs</td>
			<td>LA1134-B</td>
			<td>Newton, NJ</td>
		</tr>
		<tr>
			<td>16 mm aspherical expander lens</td>
			<td>Thorlabs</td>
			<td>AC080-016-C</td>
			<td>Newton, NJ</td>
		</tr>
		<tr>
			<td>175 mm expander lens</td>
			<td>Thorlabs</td>
			<td>LA1229-C</td>
			<td>Newton, NJ</td>
		</tr>
		<tr>
			<td>Spot blocker (cabron-steel sphere)</td>
			<td>Bal-Tec</td>
			<td>0.0100" diameter</td>
			<td>Los Angeles, CA</td>
		</tr>
		<tr>
			<td>Microspheres (Carboxyl-polystyrene)</td>
			<td>Spherotech</td>
			<td>CP-45-10</td>
			<td>Lake Forest, IL</td>
		</tr>
	</tbody>
</table>

construction of a high resolution microscope with conventional and holographic optical trapping capabilities

High resolution microscope systems with optical traps allow for precise manipulation of various refractive objects, such as dielectric beads 1 or cellular organelles 2,3, as well as for high spatial and temporal resolution readout of their position relative to the center of the trap. The system described herein has one such "traditional" trap operating at 980 nm. It additionally provides a second optical trapping system that uses a commercially available holographic package to simultaneously create and manipulate complex trapping patterns in the field of view of the microscope 4,5 at a wavelength of 1,064 nm. The combination of the two systems allows for the manipulation of multiple refractive objects at the same time while simultaneously conducting high speed and high resolution measurements of motion and force production at nanometer and piconewton scale.

The assembled setup allows the operator to trap multiple refractive objects in real time and position them in all three dimensions within the field of view. We illustrate the holographic capabilities of the instrument by trapping 11 microspheres (Figure 2). The trap confining each object is manually re-positioned upon trapping so that the final arrangement depicts the logo of the University of Utah where this experiment was performed. A combined function of holographic and conventional trap is shown in <...

Watch this Scientific Journal Video about Construction of a High Resolution Microscope with Conventional and Holographic Optical Trapping Capabilities at JoVE.com

Construction of a High Resolution Microscope with Conventional and Holographic Optical Trapping Capabilities

The system described herein employs a traditional optical trap as well as an independent holographic optical trapping line, capable of creating and manipulating multiple traps. This allows for the creation of complex geometric arrangements of refractive particles while also permitting simultaneous high-speed, high-resolution measurements of the activity of biological enzymes.

High resolution microscope systems with optical traps allow for precise manipulation of various refractive objects, such as dielectric beads 1 or cellular ...

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Research

JoVE Journal

Engineering

12.0K visualizações.  University of Utah. O sistema aqui descrito emprega uma armadilha óptica tradicional, bem como uma linha de captura óptica holográfica independente, capaz de criar e manipular múltiplas armadilhas. Isso permite a criação de disposições geométricas complexas de partículas de refração e ao mesmo tempo permitindo medições simultâneas de alta velocidade, de alta resolução da atividade de enzimas biológicas.